Mis-sized & tight armpits... - Rab Electron Pro Jacket - Men's

This jacket seems to be a great combination of warmth, packability & weight (17-17.5oz on my scale for a L and 19oz on my scale for an XL). Compared to the OR Helium Hoodie, this jacket as WAY more down, with minimal additional weight and still packs down nicely. However, some reviews across the web have mentioned the armpits are VERY tight and I'd definitely agree. I wear a large in every major brand of outdoor gear, including OR, Mountain Hardwear, TNF, REI and Rab. The Large Electron Pro fits me great with just a t-shirt and still has plenty of room to layer underneath (a base layer, mid+ weight fleece & light outer jacket fit fine underneath the electron pro). However, the armpits are so tight in the Large that it's terribly uncomfortable with just a t-shirt and worse with any additional layers underneath. An XL electron pro is way too big (no surprise, an XL is always too big in the body and sleeves from every other brand too), but the armpits are still noticeably too tight (it's borderline in the XL, but still too tight). For reference, I'm not a body builder, don't have oversized arms - just average, and have never had this issue before, even with other Rab jackets.

This is surprising to find from a company making active outdoor wear, because it's uncomfortable at rest and definitely limits the range of motion while moving. Some might think it's slim fit, but only the arms & armpits are slim fit. The body of the jacket is definitely sized regularly (not slim), so it's a really bizarre combination of sizing, leaving me wondering who this jacket would comfortably fit.

This would be a great 5+ star jacket if the sizing wasn't so far off in the armpits.